Amazon.com said Friday it’s buying its 11-building headquarters complex in South Lake Union from Vulcan Real Estate for $1.16 billion.

The sale is expected to close before the end of the year, Amazon said in a regulatory filing.

Vulcan has built the 1.8 million-square-foot complex for Amazon over the past five years. When Vulcan put the properties on the market in late August, vice president Ada Healey speculated Amazon might be among the potential buyers.

Brokers speculated at the time that the complex could fetch more than $1 billion. Amazon’s leases are scheduled to run well into the next decade.